When Jon Gosselin tried to call things off with babysitter Stephanie Santoro, he didn’t resort to the usual, “It’s not you, it’s me” line.

Instead, Jon took a more aggressive approach — he told her to stop contacting him or he would sue her.

And Jon didn’t stop there – he also threatened to sue her father!

That’s the latest bombshell from Stephanie’s mother, Marci Santoro, who told RadarOnline.com in an exclusive video interview that Jon grew hostile and aggressive at the end of the relationship.

RadarOnline.com broke the exclusive story that Stephanie, the babysitter for Jon and Kate’s eight kids, was romantically involved with Jon. Stephanie has now come out and confirmed our exclusive report.

Marci says Stephanie is still trying to get a copy of the non-disclosure agreement that Gosselin made her sign after hiring her as his children’s babysitter. To this day, Jon hasn’t delivered, and when she tries to ask him about it, he lashes out, threatening to sue. According to Marci, Stephanie never was shown the agreement and was only given a signature page, which she signed.

One of the things Jon may have wanted her to stay mum about: former Star reporter Kate Major, who Marci claims was still sending Jon text messages while he was with Stephanie. Marci says she tried to stay out of her daughter’s drama, but after Gosselin went public with his love and devotion to Hailey Glassman, she became concerned about her daughter’s well being.

Marci told RadarOnline.com: “She [Stephanie] told me that Jon would show her Kate’s text messages and that they said things like ‘you made all these promises to me, you told me you wanted to spend your life with me.'”

“I thought, ‘Here is another woman saying the same things my own daughter is telling me,'” Marci said. “Then I read in the magazines that he’s telling people he’s in love with Hailey all at the same time. I became very concerned that Stephanie was going to get hurt.”